The Kenwood SP-230 external speaker is an upgrade to the built-in speaker for various Kenwood HF rigs. Similar to my Yaesu FT-991A, the Kenwood HF rigs I have use a small internal speaker just under top cover for the built-in speaker. The audio quality of these internal speakers are limited in my opinion mainly due to the fact that they are facing upward and not forward toward the operator.

Simply moving a speaker to face forward makes a significant difference in sound quality. This is why almost any external speaker which is front facing will improve the sound quality and experience for the operator.

The SP-230 is designed to match the TS-830 and also matches the TS-530. The speaker cabinet itself is large, the same height as the rigs they match. This allows for a larger than average driver size and quite a bit of room for acoustic properties to improve sound quality versus a smaller cabinet size.

The SP-230 speaker cabinet has an A/B switch, allowing for connection to two rigs and to be able to switch between them. It also has a low filter and two high filters. These filters can be combined if needed. Adding this speaker made quite a difference, however the speaker itself is rather cheap.

Since the speaker inside the SP-230 is rather cheap, the sound quality can be improved quite a bit. My experience with this external speaker from Kenwood was similar to my Yaesu SP-10 external speaker. I had purchased the SP-10 external speaker for the FT-991A and found that its internal driver was no different from the internal speaker built into the radio. The only real difference is that the speaker is front facing versus the top facing speaker in the radio. I found the Phonema PHITS acoustic foam kit which was designed for the SP-10. It made such an improvement combined with a driver replacement I found on Amazon.

Gamma Phits GPH-X80 and Phits K95A

I purchased a similar kit for the SP-230, the Phits K95A. This is the acoustic foam kit designed to fit the SP-230, SP-930, SP-940, and SP-180. I also found the Phits GPH-X80, which is the speaker driver replacement for the SP-230, also fitting the SP-180 and Yaesu SP-767 and SP-102.

I replaced the speaker first. It was very easy to replace and everything lined up perfectly. I took the front plate off so that there was a bit more room to get the soldering iron in there. The positive connection to the speaker was just long enough to reach, so I avoided cutting too much off the end when clipping out the old speaker. There are two connections to the negative side of the speaker.

I was impressed to see a real filter circuit in this speaker. Notice how this circuit is bolted to the lower cover with short standoffs.

After replacing the speaker, I started adding the foam. The most difficult part of the process is the bottom piece of foam. I had to remove the filter circuit from the bottom cover, and remove the standoffs from the bottom cover.

The kit comes with 4 new taller standoffs. These can then be punched through the foam and the filter circuit placed higher up off the bottom cover. I used a small screwdriver from underneath the bottom cover to punch through the foam, then push (while twisting) the standoffs back down through the foam.

After adding the two foam pieces on the side and the foam piece on top, I found it to be quite a challenge to get the top cover back on. I had the exact same challenge with the SP-10 foam kit. I carefully pushed down on the top cover and placed one screw at a time until all of the screws were in place.

Results

The new speaker and foam sounded great! At first it had way too much high end, almost tinny. What I found was I had to turn the tone dial on the rig all the way to the right with the original speaker. With this replacement, the tone dial in the middle sounds best.

I just so happened to pick up a pile up on 10 meters with a station in the UK. I was able to pick out quite a few of the call signs with ease. The replacement was a success and made quite a difference.

As with any modification, I attempt to avoid permanent changes to vintage equipment. I saved the original speaker and standoffs, and can easily revert back to the original configuration if needed.

Using the Speaker for Two Transceivers

A reader of this post, N7YGU had commented that the SP-230 (or any other speaker which has an A/B source selector) can possibly cause an issue to the transceiver (or audio amplifier) which is switched out of circuit. For example, if two transceivers are connected to the SP-230, one to input A and another to input B, if input A is selected, then the other rig will see no load (an open circuit) across its audio output circuit.

While an open circuit on an audio amplifier’s output is not necessarily damaging in every case, there certainly are older circuit designs which rely on a load being present on the output terminals of the audio amplifier. This is most prevalent on audio amplifiers which use an audio transformer and/or tubes in the circuit. An open circuit could cause back EMF in the transformer, or, alter the bias on the amplifier circuit.

The SP-230 shares the same circuitry or design as the SP-180:

If we examine the circuit paths for switch S4 (input), the opposite selected input will be effectively see an open circuit across whatever circuit is connected to it.

If an 8 ohm load were to be able to be switched into the opposite selected input, then the inputs would see either an 8 ohm load from the actual speaker, or an 8 ohm (or close equivalent) dummy load when switched out from the actual speaker.

Luckily this can be accomplished quite easily, since the input switch is DPDT and has the other row completely unused:

An 8 ohm resistor can be wired in as follows:

In the schematic above, switch S4 now has an 8 ohm resistance (R4) connected to the center pin on the unused side of the DPDT switch and the other end of the resistance is connected to ground.

Pin 4 is connected to pin 3 and pin 6 is connected to pin 1. This provides the opposite selected input with a load of 8 ohms. Below is a picture of the proposed fix from N7YGU using a 10 ohm resistor:

The speaker is rated at an input of 2 watts, and therefore, if a 2 watt (or more) 8 ohm equivalent resistance can be used, this would be ideal, making sure that the resistor used for this fix is not damaged by too much heat.

It would appear that some consideration for impedance matching was thought of on the headphone side of the circuit, using R3, which is switched into circuit when the headphones are plugged in. This along with R1 and R2 provide for some level of impedance matching for headphones. However, I am not sure what Kenwood assumed the headphone impedance would be, and the owners manual does not specifically mention it. I would assume an 8 ohm load is what is expected for the headphones as well.

The owner’s manual for the SP-230 is included below:

Final Thoughts

In my opinion, the quality of the audio output of a transceiver (or receiver) is one of the most important aspects that contributes to the experience of using the radio. If the audio quality is terrible, not clear, or not balanced correctly, it makes using the radio more of a chore.

In many cases, especially with HF, having a well designed and balanced audio output can allow you to hear more of the received signal(s) at a lower volume level, and without ear fatigue. The worst possible placements for a speaker on a radio would be the bottom, back, top, or side of the enclosure. If the speaker faces the operator (usually the front), then the audio quality and experience is greatly improved.

Even though the SP-230 out of the box without any modification would be a big improvement in audio experience, adding a better speaker and performing the impedance fix as described above are simple yet provide for a rather impressive improvement.

Even though the quality of the original speaker is roughly the same as the built-in speaker, it is the placement of the speaker which makes most of the difference. Having a matching speaker cabinet also has a benefit, which justifies the (relatively low) cost of these on auction sites, used. The SP-230 is well worth the cost and effort, and provides a significant upgrade to the TS-530 and TS-830 transceivers.